U.S. patent application number 12/996095 was filed with the patent office on 2011-07-28 for ultrasonic diagnostic apparatus.
This patent application is currently assigned to HITACHI MEDICAL CORPORATION. Invention is credited to Shinichiro Kishi, Mitsuhiro Oshiki, Atsushi Suzuki.
Application Number | 20110184289 12/996095 |
Document ID | / |
Family ID | 41398141 |
Filed Date | 2011-07-28 |
United States Patent
Application |
20110184289 |
Kind Code |
A1 |
Oshiki; Mitsuhiro ; et
al. |
July 28, 2011 |
ULTRASONIC DIAGNOSTIC APPARATUS
Abstract
An ultrasonic diagnostic apparatus in accordance with the
invention includes: an ultrasonic probe in which multiple
ultrasonic vibrators for transmitting/receiving an ultrasonic wave
are arranged; a transmitter configured to provide an electric
signal to each of the vibrators in the ultrasonic probe, the
transmitter providing a square wave signal having any multiple
frequency components to the each of the vibrators, causing the
vibrators to form an ultrasonic beam; a receiver configured to
receive a reception signal obtained by transmitting the ultrasonic
beam; and a signal processor configured to form an ultrasonic image
based on the reception signal.
Inventors: |
Oshiki; Mitsuhiro; (Tokyo,
JP) ; Kishi; Shinichiro; (Tokyo, JP) ; Suzuki;
Atsushi; (Tokyo, JP) |
Assignee: |
HITACHI MEDICAL CORPORATION
Tokyo
JP
|
Family ID: |
41398141 |
Appl. No.: |
12/996095 |
Filed: |
June 3, 2009 |
PCT Filed: |
June 3, 2009 |
PCT NO: |
PCT/JP2009/060112 |
371 Date: |
April 13, 2011 |
Current U.S.
Class: |
600/443 |
Current CPC
Class: |
G01S 15/8909 20130101;
B06B 1/023 20130101; G01S 7/5202 20130101; G01S 15/8952
20130101 |
Class at
Publication: |
600/443 |
International
Class: |
A61B 8/14 20060101
A61B008/14 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 5, 2008 |
JP |
2008-148311 |
Claims
1. An ultrasonic diagnostic apparatus, characterized by comprising:
an ultrasonic probe in which multiple ultrasonic vibrators for
transmitting/receiving an ultrasonic wave are arranged; a
transmitter configured to provide an electric signal to each of the
vibrators in the ultrasonic probe, the transmitter providing a
square wave signal having any multiple frequency components to the
each of the vibrators, causing the vibrators to form an ultrasonic
beam; a receiver configured to receive a reception signal obtained
by transmitting the ultrasonic beam; and a signal processor
configured to form an ultrasonic image based on the reception
signal.
2. The ultrasonic diagnostic apparatus according to claim 1,
further comprising a switch section configured to variably set the
duty ratio of the square wave signal provided to the each of the
vibrators.
3. The ultrasonic diagnostic apparatus according to claim 2,
wherein the switch section variably sets the duty ratio of the
square wave signal with time.
4. The ultrasonic diagnostic apparatus according to claim 2,
wherein the switch section sets the duty ratio of the square wave
signal provided to the each of the vibrators differently for each
vibrator.
5. The ultrasonic diagnostic apparatus according to claim 1,
further comprising a controller configured to control the
transmitter to output the square wave signal having multiple
frequency components when tissue harmonic imaging is performed.
6. The ultrasonic diagnostic apparatus according to claim 2,
further comprising a controller configured to control the square
wave transmission circuit to variably control the duty ratio in the
period at which the transmitter provides the square wave signal to
the vibrator.
7. The ultrasonic diagnostic apparatus according to claim 2,
wherein the controller further comprises a control unit for
controlling the square wave transmission circuit for variably
controlling from a first ON-duration set in the switch section to a
second ON-duration that is different from the first ON-duration in
the period at which the transmitter provides the square wave signal
to the vibrator.
8. The ultrasonic diagnostic apparatus according to claim 2,
wherein the controller further comprises a control unit for
dividing the period at which the transmitter provides the square
wave signal to the vibrator, providing the vibrator with multiple
signals having different frequencies in those respective divided
durations of the period, and controlling the square wave
transmission circuit to variably control the duty ratio.
9. The ultrasonic diagnostic apparatus according to claim 4,
wherein the transmitter is connected to positive and negative power
sources, and wherein the positive and negative power sources
include multiple power sources.
10. The ultrasonic diagnostic apparatus according to claim 9,
characterized by further comprising a control unit configured to
control the multiple positive and negative power sources by the
switch section.
11. The ultrasonic diagnostic apparatus according to claim 1,
wherein the transmitter includes a single power source and a pulse
transformer.
Description
TECHNICAL FIELD
[0001] The present invention relates to an ultrasonic diagnostic
apparatus that can transmit a square wave and, more particularly,
to an ultrasonic diagnostic apparatus including a square wave
transmission circuit that can output a transmission signal having
multiple frequency components in one transmission.
BACKGROUND ART
[0002] An ultrasonic diagnostic apparatus transmits an ultrasonic
wave generated by an ultrasonic vibrator built in an ultrasonic
probe to an object to be tested and receives by the ultrasonic
vibrator a reflected signal generated by difference in acoustic
impedance due to hardness of a tissue of the object to display on a
monitor.
[0003] Conventionally, an arbitrary waveform amplifier is commonly
used to drive the above-described vibrator. On the other hand, as
an example of technique not using the arbitrary waveform amplifier,
Patent Document 1 discloses a transmission circuit for diagnostic
apparatus having a square wave signal amplifier circuit that can
suppress the degradation of an image obtained from harmonics
generated from within a living body or from contrast agent or the
like by reducing harmonics generation.
Prior Art Document
Patent Document
[0004] Patent Document 1: JP-A-2002-315748
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0005] However, according to the disclosure of Patent Document 1,
the square wave signal output circuit only decreases the duty ratio
of each pulse as the distance from the center to the both edges of
the amplitude of an input signal increases to suppress the
generation of high-frequency components of the envelope shape of
the pulse. So, arbitrary waveform generation by square wave signal
circuit has not been achieved yet.
[0006] It is an object of the invention to provide an ultrasonic
diagnostic apparatus that can generate an arbitrary waveform using
a square wave signal circuit.
Means for Solving the Problems
[0007] In order to achieve the above object, an ultrasonic
diagnostic apparatus in accordance with the invention is
characterized by including: an ultrasonic probe in which multiple
ultrasonic vibrators for transmitting/receiving an ultrasonic wave
are arranged; a transmitter for providing an electric signal to
each of the vibrators in the ultrasonic probe, the transmitter
providing a square wave signal having any multiple frequency
components to the each of the vibrators, causing the vibrators to
form an ultrasonic beam; a receiver for receiving a reception
signal obtained by transmitting the ultrasonic beam; and a signal
processor for forming an ultrasonic image based on the reception
signal.
[0008] According to the above configuration, an ultrasonic wave
having an arbitrary waveform can be generated using a square wave
signal circuit in which: the transmitter provides an electric
signal to each of the vibrators in the ultrasonic probe, the
transmitter providing a square wave signal having any multiple
frequency components to the each of the vibrators, causing the
vibrators to form an ultrasonic beam; the receiver receives a
reception signal obtained by transmitting the ultrasonic beam; and
the signal processor forms an ultrasonic image based on the
reception signal.
Advantage of the Invention
[0009] According to the invention, it is possible to provide an
ultrasonic diagnostic apparatus that can generate an ultrasonic
wave having an arbitrary waveform using a square wave signal
circuit.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] [FIG. 1] A schematic block configuration diagram of an
ultrasonic diagnostic apparatus in accordance with the
invention.
[0011] [FIG. 2] A configuration diagram of a square wave
transmission circuit in accordance with a first embodiment.
[0012] [FIG. 3] A current-voltage diagram of a switching element
(FET) shown in FIG. 2.
[0013] [FIG. 4] An illustration showing the control timing of the
square wave transmission circuit shown in FIG. 2.
[0014] [FIG. 5] An illustration showing the control timing of the
square wave transmission circuit in accordance with the first
embodiment.
[0015] [FIG. 6] An illustration showing the correlation between the
input signal duty ratio and the output amplitude level in the
square wave transmission circuit in accordance with the first
embodiment.
[0016] [FIG. 7A] An illustration showing the correlation between
the input signal duty ratio and the output amplitude level in the
square wave transmission circuit in accordance with the first
embodiment.
[0017] [FIG. 7B] An illustration showing the correlation between
the input signal duty ratio and the output amplitude level in the
square wave transmission circuit in accordance with the first
embodiment.
[0018] [FIG. 8] An illustration showing the correlation between the
input signal duty ratio and the output amplitude level in the
square wave transmission circuit in accordance with the first
embodiment.
[0019] [FIG. 9] An illustration showing the correlation between the
input signal duty ratio and the output amplitude level in the
square wave transmission circuit in accordance with the first
embodiment.
[0020] [FIG. 10] A configuration diagram of a square wave
transmission circuit in accordance with a second embodiment.
[0021] [FIG. 11] An illustration showing the control timing of the
square wave transmission circuit in accordance with the second
embodiment.
[0022] [FIG. 12] An illustration showing the frequency distribution
of the output signal of the square wave transmission circuit in
accordance with the second embodiment.
[0023] [FIG. 13A] Graphs showing a specific example of the input
and output signals and frequency responses thereof in the square
wave transmission circuit in accordance with the second
embodiment.
[0024] [FIG. 13B] Graphs showing a specific example of the input
and output signals and frequency responses thereof in the square
wave transmission circuit in accordance with the second
embodiment.
[0025] [FIG. 13C] Graphs showing a specific example of the input
and output signals and frequency responses thereof in the square
wave transmission circuit in accordance with the second
embodiment.
[0026] [FIG. 13D] Graphs showing a specific example of the input
and output signals and frequency responses thereof in the square
wave transmission circuit in accordance with the second
embodiment.
[0027] [FIG. 14] A configuration diagram of a square wave
transmission circuit in accordance with a third embodiment.
[0028] [FIG. 15] A configuration diagram of a square wave
transmission circuit in accordance with a fourth embodiment.
[0029] [FIG. 16] An illustration showing the input and output
waveforms of a square wave transmission circuit in accordance with
the fourth embodiment.
[0030] [FIG. 17] A configuration diagram of a square wave
transmission circuit in accordance with a fifth embodiment.
[0031] [FIG. 18] An illustration showing the input and output
waveforms of a square wave transmission circuit in accordance with
the fifth embodiment.
[0032] [FIG. 19] A configuration diagram of a square wave
transmission circuit in accordance with a sixth embodiment.
[0033] [FIG. 20] An illustration showing the input and output
waveforms of a square wave transmission circuit in accordance with
the sixth embodiment.
MODE FOR CARRYING OUT THE INVENTION
[0034] Specific embodiments of the invention are described below
with reference to the drawings. Note that, in the description, a
means may be referred to as "circuit" or "section." For example, a
control means may be referred to as "control circuit" or "control
section."
[0035] FIG. 1 is a block diagram showing an entire configuration of
an ultrasonic diagnostic apparatus for describing the specific
embodiments.
[0036] The ultrasonic diagnostic apparatus includes: an ultrasonic
probe 100 having multiple vibrators; an element selector 101
configured to select an element of the multiple vibrators; a
transmission/reception separator 102; a transmission processor 103
configured to form and transmit a transmission signal; a
transmitter 104; a reception amplifier 105 configured to amplify a
received signal from the ultrasonic probe 100; a phasing addition
processor 106; a signal processor 107 configured to perform signal
processing such as logarithmic processing on a signal from the
phasing addition processor 106; a scan converter 108 configured to
scan-convert from ultrasonic scanning to display scanning using a
signal from the signal processor 107; a display monitor 109,
including a CRT, liquid crystal display or the like, configured to
display an image data from the scan converter 108; and a controller
110 configured to control these components.
[0037] The transmission/reception separator 102 switches the signal
direction depending on whether transmission or reception is
occurring. The transmitter 104 provides a drive signal to the
multiple vibrators (not shown) in the ultrasonic probe 100 in order
to transmit an ultrasonic wave to within an object to be tested.
The transmission processor 103 includes a known pulse generator
circuit, a known amplifier circuit and a known transmission delay
circuit to provide a transmission signal to the transmitter
104.
[0038] The multiple vibrators convert reflected waves (echoes)
reflected from within the object due to an ultrasonic wave
transmitted into the object to electric signals (received signals).
The phasing addition processor 106 uses the received signals to
form and output an ultrasonic beam signal as if having received
from a predetermined direction. The phasing addition processor 106
includes a known reception delay circuit and a known adder
circuit.
[0039] The signal processor 107 performs logarithmic conversion,
filtering, gamma (.gamma.) correction and the like as preprocessing
for imaging a received signal output from the phasing addition
processor 106.
[0040] The scan converter 108 accumulates a signal output from the
signal processor 107 for each ultrasonic beam scanning to form an
image data and outputs the image data according to the scanning of
an image display device, that is, performs scan conversion from
ultrasonic scanning to display scanning.
[0041] The display monitor 109 is a display device for displaying
as an image an image data (converted to a luminance signal) output
from the scan converter 108.
[0042] The controller 110 is a central processing unit (CPU) for
directly or indirectly controlling the above-described components
to perform ultrasonic transmission/reception and image
displaying.
[0043] In the configuration of this ultrasonic diagnostic
apparatus, the ultrasonic probe 100 is touched to an area to be
tested of the object (not shown), then, a scan parameter such as
transmission focus depth is input to the controller 110, and then,
an instruction to start ultrasonic scanning is input. The
controller 110 controls the components to start ultrasonic
scanning.
[0044] The controller 110 outputs to the element selector 101 and
the transmission processor 103 an instruction to select a vibrator
to be used in the first transmission, an instruction to output a
drive pulse and an instruction to set a delay time according to the
transmission focus depth. When these instructions are executed, the
transmission processor 103 provides a drive pulse to the
transmitter 104 via a transmission delay circuit (not shown). The
transmitter 104 amplifies the drive pulse to a sufficient amplitude
for driving the multiple vibrators in the probe 100 and provides
the amplified drive pulse to the ultrasonic probe 100.
[0045] Of the vibrators in the ultrasonic probe 100, vibrators
selected by the element selector 101 and the transmitter 104 that
provides a transmission signal are connected via the
transmission/reception separator 102. When the drive pulse is
input, the vibrators vibrate at predetermined frequencies and
sequentially transmit an ultrasonic wave into the object.
[0046] When the ultrasonic wave is transmitted into the object, a
portion of the wave is reflected by a surface of a tissue or organ
in a living body at which acoustic impedance changes, toward the
ultrasonic probe 100 as echoes. The controller 110 controls the
reception chain to receive the echoes.
[0047] Specifically, first, upon finishing the transmission, the
element selector 101 performs switching selection to connect a
vibrator for reception with the phasing addition processor 106.
With this vibrator switching selection, control of reception delay
time is performed on the phasing addition processor 106.
[0048] The received signals delayed by reception delay circuits are
phased and added by the phasing addition processor 106 into a
reception beam signal that is output to the signal processor 107.
The signal processor 107 performs the above-described processing on
the received signal input from the phasing addition processor 106
and outputs the processed signal to the scan converter 108. The
scan converter 108 stores the input signal in a memory (not shown)
and reads to output the stored contents to the display monitor 109
according to a synchronization signal for displaying. Upon
finishing the above operation, the controller 110 changes the
direction of ultrasonic transmission/reception to perform the
second round of the operation, and then performs the third round
and so on. In this way, the controller 110 sequentially changes the
direction of ultrasonic transmission/reception to repeat the above
operation.
[0049] In the above described configuration, the invention relates
generally to the transmission circuit chain and, in particular, to
the transmission processor 103, the transmitter 104 and the
controller 110. Now, embodiments relating to the transmission
circuit chain are described below with reference to the
drawings.
First Embodiment
[0050] FIG. 2 shows a configuration of a square wave transmission
circuit having a single power source used in a first
embodiment.
[0051] As shown in FIG. 2, the square wave transmission circuit
includes: a power source 01 configured according to a voltage
applied to a vibrator 00 arranged in the ultrasonic probe 100; a
switch element 02 such as a field effect transistor (FET); and a
control unit 03 for ON/OFF controlling the switch element 02. In
general, in the transmission circuit for ultrasonic diagnostic
apparatus, in order to generate an ultrasonic signal sufficient for
observing within a living body from an ultrasonic vibrator, a
hundred and several tens of volts of electric signal needs to be
applied. In order to achieve this, in the transmission circuit, a
switch element capable of conducting or interrupting current
(turning to ON or OFF) according to a control voltage, such as a
high-voltage FET in general, is used.
[0052] FIG. 3 shows the output current against the input voltage of
a common FET. In the FET, the drain output current has a certain
relation with the gate input voltage. FIG. 4 shows an operation
timing of the square wave transmission circuit shown in FIG. 1. The
broken line shows a theoretical waveform. The solid line shows a
realistic waveform.
[0053] Suppose, as shown in FIG. 2, an input signal 04 as control
signal is applied to the switch 02 by the control unit 03. In order
to turn the switch 02 to ON, the input signal 04 as control signal
is set to H (high)-state (the same shall apply hereinafter). Thus,
in FIG. 4, a control signal 14 showing the switching timing of the
switch 02 shows that the switch is turned to ON twice. The control
unit 03 is directly or indirectly controlled by the transmission
processor 103 and the controller 110.
[0054] The input signal 04 (14) is intended to be a square wave as
shown by the broken line. However, in reality, it becomes a
distorted square wave as shown by the solid line under the
influence of the input capacitance of the circuit and the like.
Then, the waveform of the output signal 05 (15) as timing signal
depends on the input signal as described above. The shape of the
output waveform is further influenced by the threshold voltage and
output load of an FET element used in the switch circuit. Although
the input signal 14 is designed according to the drive capability
of a circuit for driving the switch 02, this drive capability is
assumed to be constant hereinafter.
[0055] The output signal 15 as timing signal shows the waveform of
a voltage applied to the vibrator 00. When the control signal 14 is
in H-state, the switch 02 is turned to ON, then the power source 01
supplies current to the vibrator 00. Thus, the maximum potential of
the vibrator 00 is almost the same as the potential of the power
source 01, then a signal for driving an ultrasonic wave is applied.
The vibrator 00 performs electroacoustic conversion by this applied
voltage to transmit an ultrasonic signal into the living body.
[0056] As shown in FIG. 4, the frequency of the square signal shown
by the broken line of the control signal 14 is determined by T1 in
the figure. When the control signal 14 that is input is in H-state,
the timing signal 15 is output. The control signal 14 that is input
becomes a distorted square wave as shown by the solid line under
the influence of the capacitance in the circuit and the like. The
timing signal 15 that is output also has a distorted waveform
depending on the capacitance of a load of the vibrator 00 and the
like.
[0057] In the square wave transmission circuit in accordance with
this embodiment, as shown by a signal 16 in FIG. 5, T2, the
duration in which the switch 02 is turned to ON of the period T1 of
the control signal 14 that is input is changed to T3. In other
words, the duty ratio of the waveform is changed from T2/T1 to
T3/T1. When an input voltage for causing the switch 02 to supply an
output current necessary for fully driving the output load cannot
be applied due to the change of the duty ratio, the amplitude of
the timing signal 17 that is output is limited, providing an effect
equivalent to change of the output amplitude.
[0058] In other words, the change of the duty ratio in this
embodiment controls the square wave transmission circuit to
variably control the duty ratio in the period at which the
transmitter provides the square wave signal to the vibrator or to
variably change from a first ON-duration set in the switch to a
second ON-duration that is different from the first ON-duration in
the period at which the transmitter provides the square wave signal
to the vibrator.
[0059] In this embodiment, as a result, changing the duty ratio of
the input signal without multiple power sources can variably change
the output amplitude equivalently without changing the signal
frequency.
[0060] FIG. 6 shows an example of the output waveform amplitude
changed by changing the duty ratio using this embodiment. The upper
portion of FIG. 6 shows the output signal waveform changed by
changing the duty ratio, and the lower portion shows the frequency
response of the output signal. According to the example shown in
FIG. 6, it has been recognized that reducing the duty ratio to
about 1/4 can reduce the normalized power by .DELTA.P.
[0061] As seen from the above-described embodiment, using a single
power source and changing the duty ratio of a positive input signal
can change the output waveform amplitude. However, the same also
applies to a positive and negative input signal. FIGS. 7A and 7B
show how the output amplitude and frequency response vary when the
pulse width and duty ratio of the first negative wave of the a
transmission waveform of the ultrasonic diagnostic apparatus are
changed. In FIGS. 7A and 7B, the input signal is a mixture of two
frequencies, and, in this example of three waves of waveform, the
first half (1.5 waves) consists of the lower frequency, and the
second half (1.5 waves) consists of the higher frequency. In this
example, the pulse width of the negative waveform of the input
signal is changed from t1 to t3 (thus, the duty ratio is changed)
as shown in FIG. 8. Thus, the controller divides the period at
which the transmitter provides the square wave signal to the
vibrator and provides the vibrator with multiple signals having
different frequencies in those respective divided durations of the
period to variably control the duty ratio. As shown in FIG. 9, it
has been recognized that, when the pulse width is changed from t1
to t3, the output amplitude changes from A1 to A3.
Second Embodiment
[0062] Next, a second embodiment, a case of inputting a positive
and negative input signal, is described with reference to FIGS. 10,
11 and 12. This embodiment is a square wave transmission circuit as
shown in FIG. 10, in which two power sources--positive power source
01 and a negative power source 06--are provided; a signal having
different frequencies between the positive and negative sides of
the signal is input; and this signal can be amplified to be output.
FIG. 11 is a timing chart of this embodiment. In FIG. 11, a
waveform 20 is a waveform of a control signal for one switch
circuit 02 connected to the positive power source 01. The signal
period of the waveform 20 is set to T4, then the center frequency
of the signal is 1/T4. On the other hand, a waveform 18 is a
waveform of a control signal for the other switch circuit 02
connected to the negative power source 06. The signal period of the
waveform 18 is T5, then the center frequency of the signal is 1/T5.
The control signals 18 and 20 are generated by a control unit
03.
[0063] As a result of the above, as shown in FIG. 12, an output
signal 19 shown in FIG. 11 has a frequency component 21 of 1/T4 in
the positive amplitude portion and a frequency component 22 of 1/T5
in the negative amplitude portion. Then, the frequency distribution
23 of the combined output signal 19 is obtained by adding the
frequency component 21 and the frequency component 22. This allows
even the square signal transmission circuit to output a signal
having multiple center frequencies in one transmission and to be
used in an ultrasonic diagnostic apparatus that images by tissue
harmonic imaging. Furthermore, as seen from FIG. 12, also in this
embodiment, the relation between the duty ratio and amplitude of
the signal shown by the first embodiment is maintained, so the
frequency component of the negative signal 18 with a larger duty
ratio is larger.
[0064] Note that, in tissue harmonic imaging, the transmission
signal may be generated using the technique of the invention and
applied to, for example, WO2007/111013.
[0065] FIG. 13A shows the output waveform against the input signal
having a frequency component varying with time. FIG. 13B shows the
frequency distribution of the output waveform. On the other hand,
FIG. 13C shows the output waveform of the same circuit against the
input signal having a constant frequency. FIG. 13D shows the
frequency distribution of the output waveform. It can be recognized
that, when the frequency is variably changed with time, the
frequency distribution of the output waveform spreads widely.
[0066] Thus, variably changing the frequency of the input waveform
with time can variably change the output waveform amplitude of the
signal the main component of which has the variably changed
frequency.
Third Embodiment
[0067] Next, a square wave transmission circuit in accordance with
a third embodiment is shown in FIG. 14. This square wave
transmission circuit has multiple pairs of positive and negative
power sources and the output amplitude is changed. The multiple
pairs of power sources enables finer tuning of the waveform than
one pair of positive and negative power sources. It will be obvious
that, also in this embodiment, a control unit 03 controls switches
02 each connected to the respective power sources 01, 06, 09 and 10
to change the duty ratio of the above-described input signal,
enabling the amplitude control.
Fourth Embodiment
[0068] A fourth embodiment is similar to the second embodiment in
that a square wave transmission circuit is provided in which a
signal having different frequencies between the positive and
negative sides of the signal is input and this signal can be
amplified to be output. However, this embodiment is different from
the second embodiment in that separate control units 204 and 205
are provided in place of the single control unit 03. Now, the
fourth embodiment is described below with reference to FIGS. 15 and
16.
[0069] As shown in FIG. 15, this embodiment has a circuit
configuration including two power sources--a positive power source
01 and a negative power source 06--, corresponding switches 202 and
203, and the control units 204 and 205. The positive signal of the
output signal of this circuit is output by the switch 202 connected
to the power source 01 having a positive power source value, and
the negative signal is similarly output by the switch 203 connected
to the power source 06 having a negative power source value.
Signals input to the switches 202 and 203 are generated by the
transmission processor 103 shown in FIG. 1 and input to the
switches 202 and 203 via the control units 204 and 205,
respectively.
[0070] Of the signals input to the switches, a signal 206 having a
period of T4 is input to the switch 202 and a signal 207 having a
period of T5 is input to the switch 203. Note that T4.noteq.T5. The
signals 206 and 207 input to the switches 202 and 203 have a low
amplitude. So, as described with reference to FIG. 1, in order to
drive the probe 100 to transmit an ultrasonic wave sufficient for
obtaining a signal from the living body, the signals 206 and 207
are amplified to the amplitude of the high-voltage power sources 01
and 06 by the switches 202 and 203, respectively. Accordingly, the
signals output from the switches 202 and 203 (thus, the signal
output from the transmitter 104) have the same frequencies as those
of the switch input signal 206 and 207 and the same amplitudes
(maximum amplitudes) as the voltages of the power sources 01 and
06.
[0071] Because of T4.noteq.T5, the output signal has a combination
of two frequencies rather than a single frequency. An example of
the output signal is shown by a signal 208 in FIG. 16. The signal
having the period of T4 is output on the positive side, and the
signal having the period of T5 is output on the negative side.
Fifth Embodiment
[0072] Next, a transmission circuit for ultrasonic diagnostic
apparatus in accordance with a fifth embodiment is described with
reference to FIG. 17. In this transmission circuit, the frequency
of the input signal can be variably changed in time direction (or
with time), and this input signal can be amplified to be
output.
[0073] A circuit configuration, similarly to that shown in FIG. 2,
including a single switch circuit 02 and a single power source 01
is described. For example, when an input signal 209 is input from a
control unit 03, an output signal 210 having the same period as
that of the signal 209 is output. Depending on the connection with
the power source, the phase of the output signal may be
inverted.
[0074] Suppose, in this transmission circuit configuration, the
frequency of the input signal 209 is changed with time, as shown by
a waveform 211 in FIG. 18. For example, the change is such that the
periods of the first, second and third waves are T212, T213 and
T214, respectively. Suppose, for example, T212>T213>T214
(T212.noteq.T213.noteq.T214 would be enough).
[0075] Then, as previously described, a signal shown by a waveform
215 appears as the output signal 210 of the transmission circuit,
which has the signal amplitude changing to the value of the power
source 01 and the frequency changing with time in a way similar to
the input signal 209. Thus, the frequency of the output waveform
varies with time.
Sixth Embodiment
[0076] The switch circuit has been described above by illustrating
the configurations shown in FIGS. 2, 15 and the like. However, the
arrangement of power sources and the like are not limited to the
above. For example, as shown in FIG. 19, a circuit including a
pulse transformer 221 and a single type power source may be used.
In this circuit, positive and negative signals are formed by FETs
M1 and M2, respectively. The polarity is determined by the
polarities (winding directions) of the portions of the pulse
transformer 221 connected to M1 and M2 and the polarity (winding
direction) of the portion of the pulse transformer 221 connected to
the probe 100.
[0077] With reference to this circuit, the operation of this
embodiment is described by taking an example of an input signal
having different frequencies between the positive and negative
sides of the signal.
[0078] In the circuit of this embodiment, SIG_N and SIG_P in FIG.
19 are provided as a signal input section. The switch section
corresponding to the above-described switch 02 is the FETs M1 and
M2. The polarities of the portions of the pulse transformer
connected to the switches M1 and M2 are opposite with respect to a
power source 219 (In the figure, a black circle shows a polarity.
The winding of the reactance forming the pulse transformer starts
from ). Suppose that waveforms 216 and 217 shown in FIG. 20 are
applied as input signals to SIG_P and SIG_N, respectively. When the
input signal 216 is in H-state, M1 is turned to ON. When the input
signal 217 is in H-state, M2 is turned to ON. Current flows from
the power source 219 through the element in ON-state and a current
controller 220 to the ground. The current controller 220 controls
the amount of current flowing through the switch M1 or M2 when in
ON-state.
[0079] Suppose that the turn ratio of the pulse transformer 221
shown in FIG. 19 is N1:N2:N3. N1, N2 and N3 are the numbers of
turns of the reactances connected to M1, M2 and the vibrator 100,
respectively.
[0080] Assuming that the coupling of the transformer is ideal, the
relations
V3/V1=N3/N1
V3/V2=N3/N2
exist. V1 and V2 are voltages generated at M1 and M2, respectively.
Also, V1 and V2 are provided from the power source 219. Then, the
voltage V3 generated according to the timing at which the switches
M1 and M2 turn to ON is applied to the probe 100.
[0081] In this example, the signals 216 and 217 having different
frequencies are applied as input signals. Accordingly, M1 and M2
turn to ON at different frequencies, and the output signal is
applied to the portion of the pulse transformer connected to the
probe 100 at the timing that is a mixture of timings at which M1
and M2 turn to ON. When the input signals 216 and 217 are given,
the output signal is as shown by a signal 218.
[0082] As has been described in detail above, the invention
provides a square wave signal transmission circuit in which the
amplitude of the output signal can be changed as desired by
changing the duty ratio of the input signal. Furthermore, the
square wave signal transmission circuit can output a signal having
different frequency components in any combination ratio.
[0083] Although the preferred embodiments of the ultrasonic
diagnostic apparatus and the like in accordance with the invention
have been described with reference to the accompanying drawings,
the invention is not limited to these embodiments. It is apparent
to the person skilled in the art that various variations and
modifications can be conceived without departing from the scope of
the technical spirit disclosed herein, and also it is understood
that those variations and modifications naturally fall within the
technical scope of the invention.
Description of Reference Numerals and Signs
[0084] 00 ultrasonic vibrator, 01, 06, 09, 10 power source, switch
circuit, 03 switch control unit, 04, 05, 14, 15, 16, 17 timing
waveform, 100 probe, 101 element selector, 102
transmission/reception separator, 103 transmission processor, 104
transmitter, 105 reception amplifier, 106 phasing addition
processor, 107 signal processor, 108 scan converter, 109 display
monitor, 110 controller
* * * * *